Method for controlling an automatic transmission

ABSTRACT

A method is proposed for controlling an automatic transmission driven by a prime mover in which a shift from a first transmission ratio to a second transmission ratio occurs in the form of a pull upshift or push downshift or a pull downshift or push upshift by a first clutch opening and a second clutch closing and an electronic transmission control device controls, via electromagnetic valves, the pressure curve of the first and of the second clutch during the shifting operation. The shifting operation is divided into various shifting phases, an engine intervention taking place in the load-transfer (LÜ) of the gradient-setting phase (GE), the sliding phase (GL), the gradient-reduction phase (GA) and the closing phase (S), an engine torque and/or a characteristic value that determines the engine torque being transferred from the transmission control device to an engine control device of the prime mover.

The invention relates to a method for controlling an automatictransmission driven by a prime mover in which a shift from a first to asecond transmission ratio occurs in the form of a pull upshift or a pushdownshift or as pull downshift or push upshift. A first clutch opens anda second one closes and an electronic transmission control devicecontrols, via electromagnetic valves, the pressure curve of the firstand second clutch during the shifting operation. The latter consists, inparticular, of rapid-filling, filling-equalization, load-transfer,gradient-setting, sliding, gradient-reduction and closing phases.

Such a method is known already from the Applicant's laid openapplication DE 44 24 456 A1 which is included by explicit reference inthe contents of the preamble of the instant patent application. In thepublication is particularly proposed to use this method in a grouptransmission.

From the prior art (“The Engine Intervention”—a new element of theelectronic transmission control by Manfred Schwab and Alfred Müller,Bosch, Technical Reports 7, 1983, pp. 166 to 174) is known, in general,to effect an engine intervention during a shifting operation, it beingpossible by an exactly timed controlled curve of the engine torqueduring shifting operations of an automatic transmission to optimize thecontrol of the transmission with regard to shifting comfort, servicelife of the friction elements and the transmissible power of thetransmission. By engine intervention is to be understood that all stepswhich, during a shifting operation in the transmission, allowpurposefully to modulate, especially to reduce, the engine torquegenerated by the combustion process. Due to the legislator's strictrequirement on the reaction time and the time cycle of the controlduring a total duration of the intervention of only about 500 ms, aprecise timed coordination of the shifting operation is required. Anengine intervention can be used both in upshifts and downshifts. Theprimary object of the engine intervention in upshifts is to reduce theenergy loss produced in the friction elements during the shiftingoperation by reducing the engine torque during the synchronizationprocess without interrupting the traction. The tolerance obtainedthereby can be used to increase the service life of the frictionpartners by abbreviating the grinding time.

From DE 42 09 091 A1, a method is further known already for reducing theengine torque during a gear shift in a motor vehicle. The energy torquewhich results from rotating masses to be retarded or accelerated duringa change of speed of the rotation angle of the engine determined by agear change is calculated here and the engine torque is reduced duringcoupling of the new transmission gear by the amount of the energytorque.

Methods of the above mentioned kind are subject to constant furtherdevelopment with regard to an optimal use of the engine interventionwith the smallest possible load of the shifting elements, an optimaltorque curve that takes into account the directives of the enginemanufacturer, especially in relation to the limits of the maximumpossible engine intervention with regard to mixture and exhaustconditions, the same as to the use of possible advantages in theshifting quality as result of the torque modulation.

The problem to be solved by this invention is to indicate an optimizeduse of the engine intervention with the purpose of improving theshifting quality by an engine intervention, especially by adapting theoutput torque during the slipping phase to the output torque at the endof the shift.

According to the invention, this problem is solved in a method of theabove mentioned kind by an engine intervention by reduction of theengine torque within the load-transfer, gradient setting, sliding,gradient-reduction and closing phases wherein an engine torque and/orcharacteristic value that determines the engine torque is transmittedfrom the transmission control device to an engine control device.Thereby excesses in the breaking in of the output torque in the partialload range can be advantageously presented in shifts of all kinds. Theresponse behavior or the drive dynamics of the transmission is alsoimproved especially during pull downshifts in the partial load range,the shifting element load is reduced and the shifting quality improvedin pull upshifts.

In one development of the invention is proposed that the start of theengine intervention for synchronization with the shifting pressurebuild-up in the GE and GL phases be delayed by a time step when thereaction of the engine to the engine intervention is quicker than thereaction of the transmission to pressure directives. Thereby isadvantageously obtained that the output torque be, not unnecessarilyreduced.

In reversal of the above mentioned features, it is proposed that thestart of the shifting pressure build-up for synchronization with theengine intervention in the GE and GL phases be delayed by a time stepwhen the reaction of the engine to the engine intervention is slowerthan the reaction of the transmission to pressure directives. Thereby isadvantageously obtained that unnecessary frictional loads on theshifting elements be prevented.

In a development of the invention, the dynamic engine torque M_DYN isincreased during the gradient-setting phase GE from 0 to 100%, in thesliding phase GL, it remains at 100% and in the gradient-reduction phaseGA that follows the dynamic engine torque M_DYN is again reduced from100% to 0.

When there exist outside the engine other torque-modulating aggregates,such as an electromotor, a dynamo, a fan, an air-conditioningcompressor, an additional brake, or others, the engine intervention isdistributed among the aggregates so as thereby to enlarge the limitedtorque range of the internal combustion engine.

The expression engine torque in this case extends to the sum of torquesof all aggregates engaged in the transmission input.

Other objects, features, advantages and possible utilizations of theinvention result from the description that follows of embodiments (shownin detail in the figures). All described and/or graphically shownfeatures by themselves or in any logical combinations constitute theobject of the invention independently of their compilation in the claimsand their references to preceding claims. With reference to theaccompanying drawings in which:

FIGS. 1 and 2 are the theoretical curve of the output torque during pullupshifts and push downshifts or pull downshifts and push upshifts withfull throttle and the position of the gas pedal at idling duringconstant dynamic torque M_DYN;

FIG. 3 is the theoretical curve of the differential rotational speedduring the shifting curve according to FIGS. 1 and 2;

FIGS. 4 and 5 are the theoretical curve of the output torque similar toFIGS. 1 and 2, but for the position of the gas pedal at part load withcompensation of the dynamic torque M_DYN;

FIGS. 6 and 7 are the theoretical curve of the output torque similar toFIGS. 1 and 2, but for the position of the gas pedal at part load underthe condition M_AB (GL)=M_AB (NG).

In FIGS. 1, 2 and 4 to 7 that follow is shown in each the theoreticalcurve of the output torque M_AB in the course of time, there being shownin separate figures, on one hand, the pull upshift and the pushdownshift (FIGS. 1, 4, 6) and, on the other, the pull downshift and thepush upshift (FIGS. 2, 5, 7). The time intervals in all figures areessentially provided with the same abbreviations; these are AG for thephase of the old gear, LÜ for the load-transfer phase, LÜ1 beingsituated before the gradient-setting phase and LÜ2 after thegradient-reduction phase, GE for the gradient-setting phase, GL for thesliding phase, GA for the gradient-reduction phase and S for the closingphase, the same as NG for the phase of the new gear. In addition, thetheoretical curve of the output torque M_AB without engine interventionis shown with a solid line and the theoretical curve of the outputtorque M_AB with engine intervention with a dotted line.

The output torque M_AB for full throttle and empty gas gear shifts (FIG.1 and FIG. 2) constantly maintaining the dynamic torque M_DYN proceedsas follows:

In the AG phase (FIG. 1), where the old gear still is on, the outputtorque runs constantly according to the formula M_AB=M_MOT×I_AG. In theload-transfer phase LÜ1, the output torque is linearly reduced to avalue M_AB=M_MOT×I_NG. In the gradient-setting phase GE, the outputtorque is linearly increased again by the value M_DYN×I_NG to the valueM_AB=(M_MOT+M_DYN)×I_NG. In the gradient-reduction phase GA that followsa linear reduction occurs by the value M_DYN×I_NG to the valueM_MOT×I_NG which is also kept constant in the phases LÜ2/S and NG. Bythe inventive engine intervention, a reduction of the output torque bythe value M_DYN×I_NG occurs to the value of the output torqueM_MOT×I_NG.

The lower curve (FIG. 1) of the output torque M_AB for a push downshiftwith empty gas without engine intervention makes possible only a curvewith strong push torque excess; the dotted line shown in phases GE, GLand GA is to be understood as reference line.

For a pull downshift with full throttle or push upshift with empty gas(FIG. 2), the output torque M_AB remains constant until the beginning ofthe gradient setting phase GE. In the gradient-setting phase GE withoutengine intervention, the curve of the output torque M_AB is reduced, inthe sliding phase GL, it is kept constant and in the gradient-reductionphase GA again linearly increased to the initial value, since in a pulldownshift with full throttle an engine intervention is not possible. Inthe load-transfer/closing phase LÜ2 S, the output torque is increased tothe value M_MOT×I_NG.

In a push upshift, as shown in FIG. 2, the output torque proceeds, atfirst, constant during the phases AG and LÜ1, in the phase GE, itincreases linearly to the value 0 and remains there during the phases GLand GA and then drops back linearly to a value M_AB=M_MOT×I_NG in theload-transfer phase LÜ2 S, which it maintains during the NG phase of thenew gear.

The differential rotational speed DELTA_N (FIG. 3) between start of therotational speed change (phase GE) and the end of the rotational speedchange (phase GA) proceeds, respectively, equally for all kinds ofshifts shown in the invention and is, therefore, shown in FIG. 3 only byway of example. The differential rotational speed DELTA_N in the phasesAG and LÜ1 proceeds constantly at first and then drops linearly duringthe phases GE, GL and GA to the value 0 which is maintained during thesucceeding phases LÜ2 or S and NG.

The theoretical curves of the output torque M_AB for the position of thegas pedal at part load with compensation of the dynamic torque M_DYN(FIG. 4 and FIG. 5) proceeds as follows:

For the pull upshift and push downshift, according to FIG. 4, the twocurves essentially correspond to the representations in FIG. 1, but withthe substantial difference that in the GE, GL and GA phases an engineintervention during the push downshift is now possible and thereby,after the load-transfer phase LÜ1, a torque reduction to the valueM_MOT×I_NG occurs and that value is maintained until reaching the phaseNG of the new gear and during the phase NG.

Also during the pull downshifts or push upshifts during the position ofthe gas pedal at part load (FIG. 5), an engine intervention is nowpossible so that a break in of the output torque in the phases GE, GLand GA due to an increase of the output torque M_AB is prevented or aholding of the output torque M_AB in the value of the phases AG and LÜ1is obtained. For the push upshift during the position of the gas pedalat part load with compensation of the dynamic torque M_DYN (FIG. 5), thestrong torque break in by an engine intervention can be similarlyprevented so that the output torque in the gradient-setting phase GEundergoes a slight reduction to the value M_MOT×I_NG.

The curve of the output torque M_AB for the pull upshift or pushdownshift during the position of the gas pedal at part load with thecondition that the output torque during the sliding phase M_AB (GL) beequal to the output torque of the new gear M_AB (NG), proceedsessentially similarly to the curve for pull upshift and push downshiftduring the position of the gas pedal at part load with compensation ofthe dynamic torque according to FIG. 4.

The theoretical curve of the output torque M_AB for pull downshift orpush upshift for the position of the gas pedal at part load with thecondition that the output torque in the sliding phase M_AB (NG) be thesame as the output torque in the phase of the new gear is shown in. FIG.7. It is to be understood here that the curve in the phases AG and LÜ1remains constant and in the phase GE, due to an intervention, linearlyincreases to a value M_MOT×I_NG and the latter is maintained during thesliding phase GL, the same as during the gradient-reduction phase GA,the load-transfer phase LÜ and the closing phase S until reaching thenew gear NG.

The curve of the output torque M_AB for the push upshift with partialgas with the previously mentioned conditions M_AB (GL)=M_AB (NG) isessentially equal to the curve for a push upshift according to FIG. 5.

Summarizing, it can thus be concluded that, according to the invention,the following strategies are possible for an engine intervention whereinthe output torque M_AB in the sliding phase GL can be modulated asfollows:

a) a compensation occurs of the dynamic excess or reduction of theoutput torque wherein M_Soll MAX ME=M_MOT−M_DYN,

b) the output torque M_AB in the sliding phase GL is equal to the outputtorque M_AB at the gear shift and NG where to the pull upshift, pushdownshift applies:

M_MOT ME=M_MOT and to the pull downshift, push upshift applies:

M_SOLL MAX ME=M_MOT×(I_NG/I_AG)-M_DYN,

c) in the course of time a linear change takes place of the outputtorque M_AB to the output torque at the shift and M_MOT×I_NG (middlecourse between a) and b)).

In all cases the desired engine theoretical torque is to be comparedwith the maximum adjustable engine torque, specifically during upshiftswith M_MOT MIN ME (push curve of the engine) and during downshifts withM_MOT MAX ME (full load curve), theoretical values M_SOLL MAX ME whichare each outside the setting range are to be limited to the maximumvalues.

What is claimed is:
 1. A method for controlling an automatictransmission driven by a prime mover in which a shift from a first to asecond transmission ratio occurs as one of a pull upshift, a pushdownshift, a pull downshift and a push upshift by a first clutch openingand a second clutch closing and an electronic transmission controldevice controls, via electromagnetic values, the pressure curve of thefirst and of the second clutch during the shift operation and the shiftconsists of a rapid-filling (SE), a filling-equalization (FA), aload-transfer (LÜ), a gradient setting (GE), a sliding (GL), agradient-reduction (GA) and a closing (S) phase and that within theload-transfer (LÜ), a gradient-setting (GE), the sliding (GL), thegradient-reduction (GA) and the closing (S) phases an engineintervention occurs wherein at least one of an engine torque (M_MOT) anda characteristic value that determines the engine torque is transmittedform a transmission control device to an engine control device of theprime mover, and wherein the directive of the engine intervention to theengine and the pressure directives to the transmission are jointlysynchronized when they have different time characteristics.
 2. Themethod according to claim 1, wherein the directive of the engineintervention on the engine is delayed over a time step in the phases(GE) and (GL) when the reaction characteristic of the engine to thepressure directives is quicker than that of the transmission.
 3. Themethod according to claim 1, wherein the pressure directives on thetransmission are delayed over a time step in the phases (GE) and (GL)when the reaction characteristic of the engine to the directive of theengine intervention is slower than that of the engine.
 4. A method forcontrolling an automatic transmission driven by a prime mover in which ashift from a first to a second transmission ratio occurs as one of apull upshift, a push downshift, a pull downshift and a push upshift by afirst clutch opening and a second clutch closing and an electronictransmission control device controls, via electromagnetic values, thepressure curve of the first and of the second clutch during the shiftoperation and the shift consists of a rapid-filling (SE), afilling-equalization (FA), a load-transfer (LÜ), a gradient setting(GE), a sliding (GL), a gradient-reduction (GA) and a closing (S) phaseand that within the load-transfer (LÜ), a gradient-setting (GE), thesliding (GL), the gradient-reduction (GA) and the closing (S) phases anengine intervention occurs wherein at least one of an engine torque(M_MOT) and a characteristic value that determines the engine torque istransmitted form a transmission control device to an engine controldevice of the prime mover, and wherein the directive of the engineintervention to the engine and the pressure directives to thetransmission are jointly synchronized when they have different timecharacteristics, and wherein the engine intervention occurs by directiveof an engine theoretical torque (M_SOLL) by the transmission controldevice.
 5. The method according to claim 4, wherein the directive of theengine intervention on the engine is delayed over a time step in thephases (GE) and (GL) when the reaction characteristic of the engine tothe pressure directives is quicker than that of the transmission.
 6. Themethod according to claim 4, wherein the pressure directives on thetransmission are delayed over a time step in the phases (GE) and (GL)when the reaction characteristic of the engine to the directive of theengine intervention is slower than that of the engine.
 7. The methodaccording to claim 4, wherein the engine intervention occurs bydirective of a sign-provided additional torque through the transmissioncontrol device.
 8. The method according to claim 4, wherein the engineintervention occurs by directive of a characteristic value through thetransmission control device which indicates the ratio of the enginetheoretical torque with engine intervention (M_SOLL ME) to a referencebasis.
 9. The method according to claim 4, wherein actual torque(M_STAT) is calculated according to an engine theoretical torque withengine intervention (M_SOLL ME).
 10. The method according to claim 4,wherein during downshifts a sign provided engine theoretical torque withengine intervention (M_SOLL MAX ME) is calculated according to a maximumsign-provided dynamic torque (M_DYN), to the engine torque withoutengine intervention (M_MOT) and to a maximum possible engine torque withengine intervention.
 11. The method according to claim 4, wherein duringupshifts a sign provided engine theoretical torque with engineintervention (M_SOLL MAX ME) is calculated according to a maximumsign-provided dynamic torque (M_DYN), to the engine torque withoutengine intervention (M_MOT) and to a minimum possible engine torque withengine intervention (M_MOT MIN ME).
 12. The method according to claim10, wherein the maximum engine theoretical torque with engineintervention (M_SOLL MAX ME) is calculated as sum of (M_MOT) minus(M_DYN).
 13. The method according to claim 10, wherein the maximumengine theoretical torque with engine intervention (M_SOLL MAX ME) iscalculated as sum of (M_MOT) multiplied by the ratio new gear (I_NG) bythe ratio old gear (I_AG) minus (M_DYN).
 14. The method according toclaim 12, wherein the maximum engine theoretical torque with engineintervention (M_SOLL MAX ME) is changed from the value according toclaim 8 to the value of claim 9 in the phases (GE, GL, GA, LÜ, S). 15.The method according to claim 8, wherein in the phase (GE) the enginetheoretical torque with engine intervention (M_SOLL ME) changes from thevalue of the engine torque without engine intervention (M_MOT) to thevalue of the maximum engine theoretical torque with engine intervention(M_SOLL MAX ME) in upshifts.
 16. The method according to claim 9,wherein in the phase (GE) the engine theoretical torque with engineintervention (M_SOLL ME) changes from the value of the engine torquewithout engine intervention (M_MOT) to the value of the maximum enginetheoretical torque with engine intervention (M_SOLL MAX ME) in upshifts.17. The method according to claim 4, wherein during pull downshifts andpush upshifts in the phases (GA, LÜ2 and S), the engine theoreticaltorque with engine intervention (M_SOLL ME) changes from the value ofthe maximum engine theoretical torque with engine intervention (M_SOLLMAX ME) to the value of the engine torque without engine intervention(M_MOT).
 18. The method according to claim 4, wherein during pullupshifts and push downshift in the phases (GA, LÜ2 and S), the enginetheoretical torque with engine intervention (M_SOLL ME) changes from thevalue of the maximum engine theoretical torque with engine intervention(M_SOLL MAX ME) to the value of the engine torque without engineintervention (M_MOT).
 19. The method according to claim 4, wherein theclutch pressure (P_K) on the closing clutch is calculated from thestatic engine torque with engine intervention (M_STAT ME), the dynamicengine torque (M_DYN), a factor (F1), a converter reinforcement (WV) andthe absolute pressure (P_ABS).
 20. The method according to claim 4,wherein the dynamic engine torque (M_DYN)during the gradient-settingphase (GE) is increased from zero to 100% in the sliding phase (GL),remains at 100%, and in the gradient-reduction phase (GA) is reducedfrom 100% to zero.
 21. The method according to claim 4, wherein themaximum (M_MOT MAX ME) and minimum (M_MOT MIN ME) possible engine torquewith engine intervention is actually reported back from the enginecontrol device to the transmission control device.
 22. The methodaccording to claim 4, wherein the maximum (M_MOT MAX ME) and the minimum(M_MOT MIN ME) possible engine torque with engine intervention arestored in characteristic fields in the transmission control deviceaccording to operating parameters such as engine rotational speed, loadposition, or injection amount or engine torque, or air mass.
 23. Themethod according to claim 4, wherein the engine intervention isactivated according to operating parameters such as engine rotationalspeed, load position, or injection amount or engine torque or air mass.24. The method according to claim 4, wherein when othertorque-modulating aggregates (for ex., electromotor, dynamo, fan, airconditioning compressor, additional brake) exist, the engineintervention is distributed among said aggregates.
 25. A method forcontrolling an automatic transmission driven by a prime mover in which ashift from a first to a second transmission ratio occurs as one of apull upshift, a push downshift, a pull downshift and a push upshift by afirst clutch opening and a second clutch closing and an electronictransmission control device controls, via electromagnetic values, thepressure curve of the first and of the second clutch during the shiftoperation and the shift consists of a rapid-filling (SE), afilling-equalization (FA), a load-transfer (LÜ), a gradient setting(GE), a sliding (GL), a gradient-reduction (GA) and a closing (S) phaseand that within the load-transfer (LÜ), a gradient-setting (GE), thesliding (GL), the gradient-reduction (GA) and the closing (S) phases anengine intervention occurs wherein at least one of an engine torque(M_MOT) and a characteristic value that determines the engine torque istransmitted form a transmission control device to an engine controldevice of the prime mover, and wherein the directive of the engineintervention to the engine and the pressure directives to thetransmission are jointly synchronized when they have different timecharacteristics, and wherein the clutch pressure (P_K) at the start ofthe engine intervention, namely, at the start of the phase (GE), iscalculated as the sum of the absolute pressure (P_ABS) and the staticengine pressure (P_M_STAT), the latter being calculated as product fromthe factor (F1) by the static engine torque (M_STAT) by the converterreinforcement (WV).
 26. The method according to claim 25, wherein theclutch pressure (P_K) during the sliding phase (GL) is calculated as thesum of the absolute pressure (P_ABS) and the pressure (P_M STATE ME) ofthe static engine torque with engine intervention and the pressure (P_MDYN) of the dynamic engine torque (P_M DYN) being calculated as productfrom the factor (F1) by the converter reinforcement (WV) by the dynamicengine torque (M_DYN).